A pilot study employing a synchronized paracorporeal left ventricle to aortic bypass pump in calves has demonstrated satisfactory long-term bypass and complete left ventricle decompression. The bypass pump consists of an extremely smooth, seam-free, segmented polyurethane sac surrounded by a polycarbonate shell. Ball valves are employed. A proposed research project which would greatly extend our initial observations is proposed. Additional improved pumps will be fabricated with added attention to an improved surface finish to decrease the possibility of thrombo-embolic complications. Engineering studies will include flow curves, flow visualization studies, and fatigue testing designed to thoroughly characterize the pump and optimize the pump performance. The unit will be used in calves to evaluate the long-term effects of complete left ventricle decompression with particular emphasis on preventing blood damage, thromboemboli, and infection. Left ventricular function curves will be generated with the use of an analog computer at weekly intervals and compared to detect evidence of left ventricular atrophy. Experimental myocardial infarction with left ventricular failure will be produced in calves, after which synchronous left ventricular pumping will be initiated. Serial left ventricular function curves will be performed at weekly intervals to detect changes (improvements?) in left ventricular function. Careful autopsy studies will be performed to determine the effect of pumping on the left ventricle and on infarct size. After prolonged, complication free, pumping has been satisfactorily performed in calves, cautious clinical use will be initiated.